Question

resposta de -x2-x+20=0

Answer 1

-x² - x + 20 = 0

Multiplicando todos os termos por (-1), temos

x² + x - 20 = 0

Bhaskara

ax² + bx + c = 0

a = 1
b = 1
c = -20

Δ = b² - 4ac
Δ = 1 - 4.(1).(-20)
Δ = 1 + 80
Δ = 81

x = $\frac{-b \frac{+}{-} \sqrt{b^2-4ac} }{2a}$

x = $\frac{-1 \frac{+}{-}9 }{2}$

x' = (-1+9) / 2 => x' = 8/2 => x' = 4
x" = (-1-9) / 2 => x" = -10/2 => x" = -5

S = {-5,4}